Identification of serotonergic neurons in human brain by a monoclonal antibody binding to all three aromatic amino acid hydroxylases

A monoclonal antibody, PH8, has been isolated and shown by immunocytochemistry to bind to serotonergic and catecholaminergic neurons in sections of the rat and human brain. In human brain, obtained at autopsy, particular fixation and embedding conditions eliminate the labelling of catecholaminergic neurons while leaving intact the labelling of serotonergic neurons. This property makes the antibody of potential use for structural studies of serotonergic neurons in the normal and diseased human brain. PH8 was raised to pure monkey phenylalanine hydroxylase and has been shown to bind to the 50,000 mol. wt. phenylalanine hydroxylase polypeptide. Immunocytochemical and immunochemical evidence is presented in support of the hypothesis that the labelling of serotonergic and catecholaminergic neurons results from the binding of PH8 to tryptophan and tyrosine hydroxylase, respectively.

Neural and non-neural components of the developing hypertension in genetically hypertensive rats

Blood pressures of Otago genetically hypertensive (GH) rats are higher than those of genetically related normotensive (N) rats as early as 35 days after birth. At this age, the elevation of blood pressure is entirely neurogenic, as both GH and N animals have similar blood pressures following ganglion blockade; however, by age 45 days an additional non-neural component of the hypertension has appeared, and this persists into adulthood. Chronic treatment with propranolol or atenolol (1 mg/kg/day) over days 28-90 does not attenuate the development of hypertension. Neonatal sympathectomy with guanethidine almost abolishes resting sympathetic tone even in adult (GH) animals, but does not prevent the appearance of the non-neural component of the hypertension. It is concluded that although sympathetic nervous tone contributes to the absolute level of blood pressure in GH rats, it is not a causative factor in the development of hypertension.

Involvement of uptake1 and uptake2 in terminating the cardiovascular activity of noradrenaline in normotensive and genetically hypertensive rats

1. In pithed, pancuronium-treated rats, inhibition of Uptake1 with desmethylimipramine (2.5 mg/kg i.v.) increased the time course of the pressor response to vasomotor nerve stimulation (1 and 5 Hz for 5 sec) but not the time course of the pressor response to injected noradrenaline (10 and 50 ng i.v.). 2. Subsequent inhibition of Uptake2 with metanephrine (3 mg/kg, i.v.) did not affect the time course of responses to either vasomotor nerve stimulation or injected noradrenaline. 3. It is concluded that Uptake1 but not Uptake2 is important in terminating the activity of noradrenaline released from rat vasomotor nerves and that neither process inactivates intraluminal catecholamine. 4. By contrast, chronotropic responses of rat atria to adrenergic nerve stimulation were prolonged by blockade of both Uptake1 and Uptake2, in agreement with previous evidence for involvement of both processes in terminating sino-atrial adrenergic responses. 5. Animals from the Otago strain of genetically hypertensive animals were identical to normotensives in their vascular handling of catecholamine. However, they lacked an atrial Uptake2 process. 6. This defect may be related to the high resting heart rate and abnormal cardiac catecholamine turnover observed to exist in the Otago hypertensive rats.

The effect of cigarette smoke on aryl hydrocarbon hydroxylase activity and cytochrome P450 content in rat liver and lung microsomes

Levels of activity of the enzyme aryl hydrocarbon hydroxylase and cytochrome P450 have been estimated in lung and liver of rats exposed to graded doses of cigarette smoke and in human bronchial mucosa of smokers, non-smokers and patients with lung cancer. Exposure of rats to smoke of four cigarettes increased both hepatic and pulmonary aryl hydrocarbon hydroxylase activity. Exposure to smoke of four cigarettes daily for seven and 14 days did not result in higher aryl hydrocarbon hydroxylase levels in the liver than one day's exposure, but in the lung longer exposures caused greater increases in enzyme activity. Injection of benzo(a)pyrene at two dose levels caused a much greater increase in both liver and lung aryl hydrocarbon hydroxylase than smoking. The lower dose maximally stimulated the enzyme in both organs. The changes in aryl hydrocarbon hydroxylase activity were accompanied by significant increases in both liver weight and the cytochrome P450 content of liver microsomes but the increase in cytochrome P450 did not parallel those in aryl hydrocarbon hydroxylase activity. Of 40 surgical and autopsy specimens of human lung and tracheal mucosa from smokers, non-smokers and cancer patients, only one was found to have detectable aryl hydrocarbon hydroxylase activity. The relationship between aryl hydrocarbon hydroxylase induction by cigarette smoke in human tissues and the development of bronchogenic carcinoma in smokers remains unclear.